Nucleic acid purification is necessary for most molecular diagnostics and research use only applications, including purification of fetal DNA for non-invasive prenatal diagnostics (NIPD). The extraction process has been streamlined and automated by utilizing magnetic bead- and membrane-based formats. While effective, particles and membranes have known limitations when confronted with challenging clinical matrices. For example, membranes and bead-based columns are compliant, have small pore sizes, and require some type of support in order to be processed by a centrifuge or vacuum system. The physical characteristics of membranes and bead columns result in significant fluidic resistance, which limits the type of samples that can be efficiently processed without clogging the consumable, and/or the total (input) sample volume that can be uni-directionally processed through the flow path. Conversely, magnetic particles must be distributed throughout the sample by agitation. The need to homogenously distribute magnetic particles within a solution limits the total input sample volume that can be processed with most magnetic bead consumables. Clinical sample attributes (such as viscosity or complexity) can lead to inefficient magnetic particle concentration on the side of a tube or rod. And silica fines can break off of the beads during the extraction process, losing their magnetization and contaminating the final sample.
The high demand for molecular testing for both screening and diagnostic purposes has increased the sample throughput requirements in laboratories. Automation of the processing steps from extraction through detection is paramount to relieve these sample processing burdens. With the inherent limitations of the other extraction technologies mentioned above, there still exists a need for a simple, low cost nucleic acid purification system that is amenable to automation.